1. Field of the Invention
The present invention relates to the field of biosensors. More particularly the present invention relates to methods, compositions and apparatus for a compact, portable, automated biosensor that can detect a wide variety of analytes. Movement of fluids through the biosensor may be controlled to increase the sensitivity and efficiency of analyte detection.
2. Description of Related Art
A need exists for a portable, reliable and sensitive biosensor capable of detecting a wide variety of analytes. Preferably, such a biosensor should be simple to use and sturdy enough for field use under a broad range of environmental conditions. Presently available biosensors are too bulky and fragile for field use, or are not sensitive enough to detect a variety of analytes from environmental or other field samples.
A biosensor is an apparatus that uses specific and/or selective binding interactions with one or more biomolecules (xe2x80x9cligandsxe2x80x9d), such as peptides, proteins, enzymes, antibodies, receptors, nucleic acids, aptamers, etc. to detect one or more target molecules (xe2x80x9canalytesxe2x80x9d). Binding of the target molecule to the ligand results in a signal that can be used to detect or quantify the analyte present in a sample. A wide variety of biosensors of different design are known. Typically, these are designed for use in clinical or research laboratories and tend to be very bulky and relatively fragile. For example, U.S. Pat. No. 6,258,606 discloses a multiplexed active biologic electrode array, allowing a variety of protein or nucleic acid biomolecules to be attached to specific locations on an integrated circuit chip. The biomolecules are exposed to samples and binding of various analytes to specific locations on the chip may be detected, for example, by fluorescence spectroscopy. In its commercial form, the biosensor is too bulky and fragile for use under field conditions.
U.S. Pat. No. 6,277,627 discloses a glucose biosensor comprising a genetically engineered glucose binding protein. The binding protein is modified to allow introduction of environmentally sensitive reporter groups. The biosensor is limited to detection of glucose or its close structural analogs and is not suited for detecting a wide variety of analytes.
U.S. Pat. No. 6,294,392 discloses a flow-through microchannel (capillary) biosensor that is said to be suitable for the detection of multiple different analytes in a sample by binding to complementary biomolecules immobilized on the wall of the microchannel. Following initial binding, immobilized complexes are denatured and flow past a downstream detector. The use of microchannels with small cross-sectional diameters would result in frequent clogging of the apparatus unless samples are first processed to remove particulate contaminants. The biosensor is not usable with relatively unprocessed samples that could clog the microchannels.
U.S. Pat. No. 6,171,238 discloses a portable hand-held biosensor device for examination of whole blood, urine and other biological liquids. The system contains a single measuring electrode that can be covered by a biodiaphragm, limiting detection to single analytes at a time. It is not capable of analyzing multiple samples for the presence of multiple analytes simultaneously.
U.S. Pat. No. 6,192,168 discloses a multimode waveguide device and fluidics cube apparatus that may be used as a biosensor. The waveguide may be attached to different biomolecules for detecting various analytes and may contain multiple channels for processing more than one sample at a time. The manufacturing process is complex, involving the machining of multiple layers before assembly into a fluidics cube. The use of a patterned reflective coating on the waveguide increases the cost and complexity of manufacture and may be limiting for the types of chemistry used to bind molecules to the waveguide surface. Non-turbulent fluid flow through the sample channels, the absence of optimized biomolecule attachment sites, and the lack of fixed internal standards result in decreased sensitivity and efficiency of detection. The use of a bezel and gasket to seal the waveguide to the fluidics cube may result in deformation of channels or damage to the waveguide due to improper tightening.
There is a need for portable biosensors that operate reliably with environmental and clinical samples, with minimal sample preparation required before analysis. Such a biosensor should be automated for simple field use and should be sufficiently compact and sturdy to function reliably while subject to jostling, shaking, and extremes of temperature and humidity that may occur in the field. Preferably, the biosensor is capable of analyzing multiple samples for the presence of multiple analytes simultaneously.